I was deeply saddened to learn last week that Sir DavidMacKay has passed away. Over the last nine months, he struggled with cancer, and documented this journey in great detail on a personal blog. He is survived by his wife and two kids, aged one and four. He was just a few days short of his 49th birthday.

I first met David MacKay at Princeton in 2006 when he gave a talk about a piece of HCI software called Dasher that he had designed. I immediately loved his presentation style, and I loved how with Dasher, he had blended theory with practical impact. He had a way to infuse a serious technical talk with wit and humor. Dasher was born out his realization that natural language can be compressed and that this compression can be presented visually as a form of text entry. From what I later read, Dasher went on to prove tremendously useful to the disabled. Soon after I got hold of a copy of David's book Information Theory, Inference and Learning Algorithms, considering it good enough to own in print, despite the fact that had made it available online for free. The amount of detail in the book in the way of examples is truly astonishing. It is a great book to learn ideas in the information sciences from first principles. His book was influential in giving me the confidence to study machine learning seriously towards the end of my PhD, because it served as a bridge from information and coding theory, which I was comfortable with. Around 2013 I learnt that dasher was available as an iOS app and I immediately installed it. A few years later I came across David's work on Gaussian processes and Bayesian learning. I remember enjoying watching this video on videolectures.net in which he explains Gaussian processes in his characteristic style -- very clear on technicals, witty and humorous, and loaded with demos and code snippets in Matlab. A while later I learnt of his book on climate change and remember browsing through the free copy he had put online.

Although I did not get too many opportunities to interact with him, David's work was, and continues to be, hugely inspiring. The world is a lesser place without him.